This invention relates to a marine propulsion unit universal drive assembly, and more particularly to an arrangement wherein a circumferential bellows encircles the universal drive coupling which permits all-direction pivoting of the stern drive unit.
It is known to provide a flexible bellows around the universal joint connecting a marine stern drive unit to an inboard engine. See, for example, U.S. Pat. Nos. 3,136,285 and 4,201,391. In the latter patent, the bellows is attached to a stationary tubular extension on the gimbal ring housing, thus necessitating sufficient clearance between the bellows and the universal joint rotating therewithin. Furthermore, in known devices of the '391 type, grease fittings have been required in the universal joint to provide lubrication to the joint bearings. This type of lubricating is not maintenance free, and the joint area usually has to be serviced on a regular basis. Furthermore, undesirable heat buildup has been observed in the joint of devices of the '391 type.
It is a task of the present invention to reduce the required diameter of the bellows without having to change the dimensions of the universal joint itself, thus making it possible to devise a more compact stern drive. It is a further task of the invention to eliminate the need for grease fittings and the like, and to provide for a more maintenance free joint arrangement while providing fully adequate lubrication therefor. It is yet another task to effectively reduce heat buildup in the area of the joint.
In accordance with the various aspects of the invention, a marine propulsion device is provided wherein the flexible bellows surrounding the universal joint disposed between a marine engine and a stern drive unit is mounted to rotate with the universal joint itself. The universal joint is disposed within a chamber delineated by the bellows itself and by end caps mounted to the universal joint shafts. Supports for the universal joint bearings are constructed to permit free flow of fluid around the bearings. A quantity of lubricating oil is supplied to the chamber and at least partially fills the chamber when the latter is at rest. Upon driving rotation of the device, the bellows and universal joint and lubricating oil all rotate together. The resultant centrifugal force causes the oil to flow radially outwardly through the bearing supports to lubricate the bearings, with the oil forming a rotating mass engaging the inner bellows face. To support the bellows against the rotating mass, a helical spring is mounted externally of the bellows and within the bellows convolutions, with the spring being anchored adjacent both ends of the bellows. In addition, the bellows functions as a finned heat radiator.